The first post office in Oshkosh was established in 1840 with John P. Gallup as postmaster, and indeed, only employee. Mail arrived weekly, with frequency increasing over the years. Early post offices shared a building with other businesses. After the Great Fire of 1875, a building designed for the purpose was built on Washington Street between Main and Jefferson. That building was used until a larger building was built in 1890 to serve as post office, federal court house, and home to other federal offices. During World War I, for instance, the draft board was based in that building.
By the 1920s, with the growth of Oshkosh, a newer building was needed. This site was purchased in 1928, and the building was opened for use in February 1931. The interior featured red tile floor and marble walls. The exterior is of Bedford stone, with green trim.
As with the earlier building, the second floor contained other federal offices including the IRS, Navy recruiter, veterans’ services office, and a room for administering civil service examinations.